Prosthetic mitral valve with tissue anchors

ABSTRACT

Apparatus and methods are described including a prosthetic atrioventricular valve ( 10 ) for coupling to a native atrioventricular valve ( 12 ). The prosthetic valve includes a support frame ( 20 ) and a covering ( 22 ), which at least partially covers the support frame. The support frame and the covering are shaped so as to define a downstream skirt ( 24 ). A plurality of prosthetic leaflets ( 40 ) are coupled to at least one element selected from the group consisting of: the support frame and the covering. An elongated anchoring member ( 152 ) is positioned around the downstream skirt in a subvalvular space ( 150 ), such that the anchoring member presses native leaflets ( 30 ) of the native valve against the downstream skirt, thereby anchoring the prosthetic valve to the native valve. Other applications are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from U.S. ProvisionalApplication 61/312,412, filed Mar. 10, 2010, entitled, “Prostheticmitral valve with tissue anchors,” which is assigned to the assignee ofthe present application and is incorporated herein by reference.

The present application is related to an international patentapplication entitled, “Prosthetic mitral valve with tissue anchors,”filed on even date herewith, which is assigned to the assignee of thepresent application and is incorporated herein by reference.

FIELD OF EMBODIMENTS OF THE INVENTION

Embodiments of the present invention relate in general to valvereplacement. More specifically, embodiments of the present inventionrelate to prosthetic valves for minimally-invasive replacement of anatrioventricular valve.

BACKGROUND

Ischemic heart disease causes regurgitation of a heart valve by thecombination of ischemic dysfunction of the papillary muscles, and thedilatation of the ventricle that is present in ischemic heart disease,with the subsequent displacement of the papillary muscles and thedilatation of the valve annulus.

Dilation of the annulus of the valve prevents the valve leaflets fromfully coating when the valve is closed. Regurgitation of blood from theventricle into the atrium results in increased total stroke volume anddecreased cardiac output, and ultimate weakening of the ventriclesecondary to a volume overload and a pressure overload of the atrium.

SUMMARY OF APPLICATIONS

For some applications of the present invention, a collapsible prostheticvalve is configured for implantation in and/or at least partialreplacement of a native atrioventricular valve of a patient, such as anative mitral valve or a native tricuspid valve. The prosthetic valve isconfigured to assume a collapsed state for minimally-invasive deliveryto the diseased native valve, such as by percutaneous or transluminaldelivery using one or more catheters. The prosthetic valve comprises acollapsible flexible support, which is at least partially covered by acovering. The prosthetic valve is shaped so as to define a downstreamskirt and an upstream annular skirt. The downstream skirt is configuredto be placed at the native valve, such that the downstream skirt passesthrough the orifice of the native valve and extends towards, and,typically partially into, a ventricle. The downstream skirt typicallypushes aside and presses against the native leaflets of the nativevalve, which are typically left in place during and after implantationof the prosthetic valve. The upstream annular skirt is configured to beplaced around a native annulus of the native valve, and to extend atleast partially into an atrium such that annular skirt rests against thenative annulus.

There is therefore provided, in accordance with some applications of thepresent invention, apparatus including a prosthetic atrioventricularvalve for coupling to a native atrioventricular valve, the prostheticvalve including:

-   -   a support frame;    -   a covering, which at least partially covers the support frame,        the support frame and the covering being shaped so as to define        a downstream skirt;    -   a plurality of prosthetic leaflets, coupled to at least one        element selected from the group consisting of: the support frame        and the covering; and    -   an elongated anchoring member, configured to be positioned        around the downstream skirt in a subvalvular space, such that        the anchoring member presses native leaflets of the native valve        against the downstream skirt, thereby anchoring the prosthetic        valve to the native valve.

For some applications, the elongated anchoring member is configured tobe positioned completely around the downstream skirt.

For some applications, the prosthetic valve further includes acontracting housing shaped so as to define a channel therethrough, afirst end of the anchoring member is fixed to the contracting housing,and a second end of the anchoring member passes through the channel.

For some applications, the prosthetic valve is configured to assumecollapsed and expanded states.

There is further provided, in accordance with some applications of thepresent invention, apparatus including a prosthetic atrioventricularvalve for coupling to a native atrioventricular valve, the prostheticvalve including:

-   -   a support frame;    -   a covering, which at least partially covers the support frame,        the support frame and the covering being shaped so as to define        a downstream skirt;    -   a plurality of prosthetic leaflets, coupled to at least one        element selected from the group consisting of: the support frame        and the covering; and    -   a plurality of subvalvular anchoring elements, coupled to the        downstream skirt, and configured to anchor the prosthetic valve        to the native valve by piercing native leaflets of the native        valve, passing through to a subvalvular space, and applying a        force against the ventricular surface of the native leaflets.

For some applications, the prosthetic valve is configured to assumecollapsed and expanded states.

For some applications, each of the tissue coupling elements is shaped asan element selected from the group consisting of: a hollow needle, asolid needle, a rod, and a rectangular plate.

For some applications, the tissue coupling elements are configured toassume a curved shape when in resting states.

For some applications, the tissue coupling elements are shaped so as todefine respective barbs.

For some applications, the tissue coupling elements include needles.

For some applications, the needles are configured to assume curvedshapes when in resting states.

For some applications, the needles are shaped so as to define respectivelumens, and the apparatus further includes an implantation tool, whichincludes a plurality of rigid rods initially positioned in the lumens,respectively, so as to at least partially straighten the needles.

For some applications, the needles include a shape memory alloy.

There is additionally provided, in accordance with some applications ofthe present invention, apparatus including a prosthetic atrioventricularvalve for coupling at a native valve, the prosthetic valve including:

-   -   a support frame;    -   a covering, which at least partially covers the support frame,        the support frame and the covering being shaped so as to define        an upstream annular skirt;    -   a plurality of prosthetic leaflets, coupled to at least one        element selected from the group consisting of: the support frame        and the covering;    -   a plurality of longitudinal members, coupled to the upstream        annular skirt at respective sites; and    -   a plurality of tissue anchors, configured to be guided along the        longitudinal members, respectively, and to couple the upstream        annular skirt to cardiac tissue in a vicinity of the native        valve.

For some applications, the prosthetic valve is configured to assumecollapsed and expanded states.

For some applications, the tissue anchors are configured to pass overthe respective longitudinal members.

For some applications, the longitudinal members include respectivewires, and the tissue anchors are configured to be guided along therespective wires.

For some applications, each of the tissue anchors includes a couplingelement that is shaped so as to define a shape selected from the groupconsisting of: a helix, a spiral, a corkscrew, and a screw shaft.

For some applications, the longitudinal members are removably coupled tothe upstream annular skirt at the respective sites.

For some applications, the prosthetic valve further includes adownstream skirt.

For some applications, the prosthetic valve further includes aventricular anchoring assembly, which includes:

-   -   a ventricular tissue anchor; and    -   a ventricular longitudinal member, a first end of which is        coupled to the support structure, and a second end of which is        coupled to the ventricular tissue anchor.

There is further provided, in accordance with some applications of thepresent invention, a method including:

-   -   providing a prosthetic atrioventricular valve, which        includes (a) a support frame, (b) a covering, which at least        partially covers the support frame, the support frame and the        covering being shaped so as to define a downstream skirt, (c) a        plurality of prosthetic leaflets, coupled to at least one        element selected from the group consisting of: the support frame        and the covering, and (d) an elongated anchoring member;    -   placing the prosthetic valve at a native valve of a subject,        such that the downstream skirt passes through an orifice of the        native valve toward a ventricle of the subject; and anchoring        the prosthetic valve to the native valve by positioning the        elongated anchoring member around the downstream skirt in a        subvalvular space, such that the anchoring member presses native        leaflets of the native valve against the downstream skirt.

For some applications, the prosthetic valve further includes acontracting housing shaped so as to define a channel therethrough, afirst end of the anchoring member being fixed to the contractinghousing, and a second end of the anchoring member passing through thechannel, and anchoring further includes pulling on the second end of theanchoring member to tighten the anchoring member around the nativeleaflets.

For some applications, placing the prosthetic valve includes deliveringthe prosthetic valve to the native valve while the prosthetic valve isin a collapsed state in a catheter, and deploying the prosthetic valvefrom the catheter such that prosthetic valve assumes an expanded state.

There is further provided, in accordance with some applications of thepresent invention, a method including:

-   -   providing a prosthetic atrioventricular valve, which        includes (a) a support frame, (b) a covering, which at least        partially covers the support frame, the support frame and the        covering being shaped so as to define a downstream skirt, (c) a        plurality of prosthetic leaflets, coupled to at least one        element selected from the group consisting of: the support frame        and the covering, and (d) a plurality of subvalvular anchoring        elements, coupled to the downstream skirt;    -   placing the prosthetic valve at a native valve of a subject,        such that the downstream skirt passes through an orifice of the        native valve toward a ventricle of the subject; and    -   anchoring the prosthetic valve to the native valve by causing        the subvalvular anchoring elements to pierce native leaflets of        the native valve, pass through to a subvalvular space, and apply        a force against the ventricular surface of the native leaflets.

For some applications, placing the prosthetic valve includes deliveringthe prosthetic valve to the native valve while the prosthetic valve isin a collapsed state in a catheter, and deploying the prosthetic valvefrom the catheter such that the prosthetic valve assumes an expandedstate.

For some applications, placing includes placing the prosthetic valvesuch that the downstream skirt pushes aside and presses against thenative leaflets.

For some applications, the needles are shaped so as to define respectivelumens, and anchoring includes causing the subvalvular anchoringelements to pierce the native leaflets while a rigid rods are initiallypositioned in the lumens, respectively, so as to at least partiallystraighten the needles, and subsequently withdrawing the rods from thelumens.

There is further provided, in accordance with some applications of thepresent invention, a method including:

-   -   providing a prosthetic atrioventricular valve, which        includes (a) a support frame, (b) a covering, which at least        partially covers the support frame, the support frame and the        covering being shaped so as to define an upstream annular        skirt, (c) a plurality of prosthetic leaflets, coupled to at        least one element selected from the group consisting of: the        support frame and the covering, and (d) a plurality of        longitudinal members, coupled to the upstream annular skirt at        respective sites;    -   placing the prosthetic valve at a native valve of a subject,        such that the upstream annular skirt rests against a native        annulus of the native valve, and the longitudinal members extend        into an atrium of the subject;    -   guiding a plurality of tissue anchors along the longitudinal        members, respectively; and    -   using the anchors, coupling the upstream annular skirt to        cardiac tissue in a vicinity of the native valve.

For some applications, the method further includes decoupling theelongated members from the upstream annular skirt.

For some applications, the method further includes, after placing theprosthetic valve at the native valve and before coupling the upstreamannular skirt to the cardiac tissue using the tissue anchors,temporarily anchoring the prosthetic valve to a ventricular wall of thesubject using one or more ventricular cords.

For some applications, placing the prosthetic valve includes deliveringthe prosthetic valve to the native valve while the prosthetic valve isin a collapsed state in a catheter, and deploying the prosthetic valvefrom the catheter such that the prosthetic valve assumes an expandedstate.

For some applications, placing the prosthetic valve includes placing theprosthetic valve at the native valve such that the longitudinal memberspass through the catheter.

For some applications, the prosthetic valve further includes adownstream skirt, and placing includes placing the prosthetic valve atthe native valve such the downstream skirt passes through an orifice ofthe native valve toward a ventricle of the subject.

For some applications, placing includes placing the prosthetic valvesuch that the downstream skirt pushes aside and presses against nativeleaflets of the native valve.

The present invention will be more fully understood from the followingdetailed description of applications thereof, taken together with thedrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a collapsible prosthetic valve, inaccordance with an application of the present invention;

FIGS. 2A-B are schematic illustrations of a technique for anchoring theprosthetic valve of FIG. 1 at a native valve, in accordance with anapplication of the present invention;

FIGS. 3A-B are schematic illustrations of another technique foranchoring the prosthetic valve of FIG. 1 at the native valve, inaccordance with an application of the present invention;

FIGS. 4A-C are schematic illustrations of yet another technique foranchoring the prosthetic valve of FIG. 1 at the native valve, inaccordance with respective applications of the present invention;

FIGS. 5A-C are schematic illustrations of additional techniques foranchoring the prosthetic valve of FIG. 1 at the native valve, inaccordance with respective applications of the present invention;

FIG. 6 is a schematic illustration of yet another technique foranchoring the prosthetic valve of FIG. 1 at the native valve, inaccordance with an application of the present invention;

FIG. 7 is a schematic illustration of still another technique foranchoring the prosthetic valve of FIG. 1 at the native valve, inaccordance with an application of the present invention; and

FIGS. 8A-G are schematic illustrations of a valve contraction tool and aprocedure for the use thereof, in accordance with an application of thepresent invention.

DETAILED DESCRIPTION OF APPLICATIONS

FIG. 1 is a schematic illustration of a collapsible prosthetic valve 10,in accordance with an application of the present invention. Prostheticvalve 10 is configured for implantation in and/or at least partialreplacement of a native atrioventricular valve 12 of a patient, such asa native mitral valve or a native tricuspid valve. The prosthetic valveis typically configured to assume a collapsed state forminimally-invasive delivery to the diseased native valve, such as bypercutaneous or transluminal delivery using one or more catheters. FIG.1 and the other figures show the prosthetic valve in an expanded stateafter delivery to the native valve.

Prosthetic valve 10 comprises a collapsible flexible support frame 20,which is at least partially covered by a covering 22. The prostheticvalve is shaped so as to define a downstream skirt 24 and an upstreamannular skirt 26. The downstream skirt is configured to be placed atnative valve 12, such that the downstream skirt passes through theorifice of the native valve and extends towards, and, typicallypartially into, a ventricle 28. The downstream skirt typically pushesaside and presses against native leaflets 30 of native valve 12, whichare typically left in place during and after implantation of theprosthetic valve. The upstream annular skirt is configured to be placedaround a native annulus 32 of the native valve, and to extend at leastpartially into an atrium 34 such that annular skirt rests against thenative annulus. The annular skirt is typically too large to pass throughthe annulus, and may, for example, have an outer diameter of between 30and 60 mm.

For some applications, collapsible support frame 20 comprises a stent,which comprises a plurality of struts. The struts may comprise, forexample, a metal such as Nitinol or stainless steel. For someapplications, covering 22 comprises a fabric, such as a woven fabric,e.g., Dacron. Covering 22 is typically configured to cover at least aportion of downstream skirt 24, and at least a portion of upstreamannular skirt 26, such as the entire annular skirt (as shown in FIG. 1).The covering may comprise a single piece, or a plurality of pieces sewntogether.

Prosthetic valve 10 further comprises a plurality of valve leaflets 40,which may be artificial or tissue-based. The leaflets are typicallycoupled to an inner surface of the valve prosthesis, such as near thejunction between the downstream and upstream skirts 24 and 26. Theleaflets are coupled, e.g., sewn, to frame 20 and/or covering 22. Forapplications in which the prosthetic valve is configured to be implantedat the native mitral valve, the prosthetic valve typically comprisesthree leaflets 40, such as shown in FIG. 1.

For some applications, such as shown in FIG. 1, prosthetic valve 10comprises a plurality of tissue anchors 50 for coupling the prostheticvalve to native valve 12, such as the mitral valve. The anchors aretypically distributed approximately evenly around upstream annular skirt26, and couple the upstream skirt to native annulus 32. Typically, eachof anchors 50 comprises a tissue-coupling element 52 coupled to a base54. Tissue-coupling element 52 is configured to pass through upstreamannular skirt 26 and penetrate the tissue of the native annulus, andmay, for example, be shaped as a corkscrew, spiral, helix, or screwshaft. Base 54 is configured to be too large to pass through theupstream annular skirt. The tissue-coupling element is advanced into thetissue, such as by rotation, until the base comes in contact with and isheld tightly against the upstream side of the upstream annular skirt,thus creating a seal between the upstream skirt and the native annulus.For some applications, prosthetic valve 10 comprises between 5 and 20anchors, such as between 10 and 15 anchors, e.g., 15 anchors. It isnoted that, unlike in some prior techniques for coupling prostheticvalves to native valve sites, sutures are typically not used forcoupling prosthetic valve 10 to the native valve site.

Reference is now made to FIGS. 2A-B, which are schematic illustrationsof a technique for anchoring prosthetic valve 10 at native valve 12, inaccordance with an application of the present invention. In thisapplication, prosthetic valve 10 is at least initially coupled to aplurality of flexible elongated members 70, such as wires, cords, orsutures. Elongated members 70 are typically removably coupled toupstream annular skirt 26 at respective sites at which respectiveanchors 50 subsequently pass through the skirt.

As shown in FIG. 2A, during an implantation procedure, the surgeonplaces prosthetic valve 10 at a desired location at native valve 12.Elongated members 70 extend into atrium 34, and typically pass through acatheter 72 used to perform the implantation procedure, optionally thesame catheter through which prosthetic valve 10 is deployed into theatrium. Optionally, the prosthetic valve is temporarily held in placeusing the anchoring techniques described hereinbelow with reference toFIGS. 4A-C (or permanently held in place using such anchoring, incombination with the anchoring described hereinbelow with reference toFIG. 2B). For example, the prosthetic valve may be temporarily anchoredto the ventricular wall, such as to the apex or one or more papillarymuscles, using one or more ventricular cords, as described hereinbelow.

Subsequently, as shown in FIG. 2B, each of anchors 50 is guided along(e.g., passed over, or alongside) a respective one of elongated members70, until the anchor reaches upstream annular skirt 26. The anchor iscoupled to cardiac tissue, such as by using a rotation tool 71 that isseparately passed over each of elongated members 70. Typically, theelongated member is then decoupled from upstream annular skirt 26. Forexample, a cutting tool may be used to decouple the elongated memberfrom the skirt; the cutting tool may be passed through catheter 72,and/or guided along the elongated member. Alternatively, the elongatedmember may be looped through the skirt, such that both ends of theelongated member remain outside of the patient's body. The surgeondecouples the elongated member from the skirt by releasing one end ofthe elongated member and pulling on the other end, until the elongatedmember is drawn from the skirt. Alternatively, the elongated member iscut at some distance from upstream annular skirt 26, such that a portionof the elongated member remains coupled to the upstream annular skirt.These steps are repeated for each of the anchors and elongated members.

These techniques enable the surgeon to readily bring the anchors to theappropriate sites of the upstream annular skirt, without the need forexcessive imaging, such as fluoroscopy.

Reference is made to FIGS. 3A-B, which are schematic illustrations ofanother technique for anchoring prosthetic valve 10 at native valve 12,in accordance with an application of the present invention. In thisapplication, anchors 50 are initially coupled to respective flexibleelongated members 70, such as wires, cords, or sutures. For someapplications, each of the anchors comprises an upstream post 73, towhich a respective elongated member 70 is coupled. Optionally, the postscomprise a flexible material, such as silicone.

As shown in FIG. 3A, during an implantation procedure, the surgeoncouples anchors 70 to respective sites of cardiac tissue on nativeannulus 32. For example, the surgeon may use a rotation tool passedalong (e.g., over or alongside) each of elongated members 70.

Subsequently, as shown in FIG. 3B, the surgeon passes prosthetic valve10 over elongated members 70, until the prosthetic valve reaches thenative valve and upstream annular skirt 26 rests against the atrial sideof native annulus 32. In order to guide the prosthetic valve to theanchors and desired anatomical position, elongated members 70 passthrough respective locations on upstream annular skirt 26. Upstreamannular skirt 26 is then coupled to the anchors, e.g., posts 73 thereof,to hold the prosthetic valve in place at the native annulus, creating aseal between the upstream skirt and the native annulus. This anchoringtechnique typically reshapes the native annulus to assume a roundershape, similar to that of the prosthetic valve.

For some applications, respective coupling elements 74 are used tocouple the skirt to the posts of the anchors. The coupling elements maybe passed over elongated members 70. For example, the coupling elementsmay be shaped as discs with inwardly-facing teeth that engage the posts,and prevent removal of the disc from the posts. The elongated membersare subsequently decoupled from anchors 50. For example, a cutting toolmay be used to decouple the elongated members from the anchors; thecutting tool may be passed through catheter 72, and/or guided along theelongated member. Alternatively, the elongated members may be loopedthrough the anchors, such that both ends of each elongated member remainoutside of the patient's body. The surgeon decouples the elongatedmember from the anchor by releasing one end of the elongated member andpulling on the other end, until the elongated member is drawn from theanchor.

Reference is made to FIGS. 4A-C, which are schematic illustrations ofanother technique for anchoring prosthetic valve 10 at native valve 12,in accordance with respective applications of the present invention. Inthese applications, prosthetic valve 10 is held in place at native valve12 by a ventricular anchoring assembly. The ventricular anchoringassembly comprises one or more ventricular longitudinal members, such asventricular cords 102, and one or more respective ventricular tissueanchors 50, described hereinabove. The ventricular cords are coupled,using the respective anchors, to respective ventricular sites, such asrespective papillary muscles 100 (as shown in FIGS. 4A-C) or otherlocations of the ventricular wall, such as near the apex of ventricle 28(configuration not shown). The cords pull prosthetic valve 10 towardventricle 28, such that upstream annular skirt 26 is pulled tightlyagainst native annulus 32. As mentioned above, the upstream annularskirt is too large to pass through the native annulus, and is thus heldin place by the cords.

For some applications, in order to tense ventricular cords 102,prosthetic valve 10 and upstream portions 110 of the cords areconfigured to provide one-way upstream motion of the cords with respectto the prosthetic valve, and to prevent distal motion of the cords. Forexample, upstream portions 110 of the cords may be shaped so as todefine a one-way ratchet, which can pass through upstream annular skirt26 in an upstream direction, but not in a downstream direction. Afterthe cords have been anchored to the ventricular sites and the prostheticvalve has been placed in position at the native annulus, the surgeonpulls upstream on the upstream ends of the cords, in order to tense thecords. Optionally, as shown in FIGS. 4B and 4C, upstream annular skirt26 comprises ratcheting elements 112, through which ratcheted upstreamportions 110 of ventricular cords 102 pass, in order to prevent suchdownstream motion.

For some applications, in order to provide access to anchors 50 duringcoupling of the anchors to the ventricular sites, the surgeon firstintroduces the anchors and cords into the ventricle, thereafter couplesthe anchors to the ventricular sites, and subsequently positions theprosthetic valve at the native annulus. The cords may pass betweendownstream skirt 24 and native leaflets 30 (as shown in FIGS. 4A-C), orthrough the downstream skirt (configuration not shown).

For some applications, as shown in FIG. 4C, the surgeon crosses cords102 in the ventricle, such that the cords assume an X-shape when viewedfrom the side. Such crossing may provide firmer anchoring of theprosthetic valve to the native annulus.

For some applications, the coupling techniques described with referenceto FIGS. 4A-C effect ventricular remodeling, in addition to or insteadof anchoring the prosthetic valve to the native valve site.

For some applications, instead of being coupled to upstream annularskirt 26 (as shown in FIGS. 4A-C), cords 102 are alternatively oradditionally coupled to downstream skirt 24, such as to struts of thesupport frame thereof, e.g., at or near a downstream end of thedownstream skirt (configuration not shown).

Reference is made to FIGS. 5A-C, which are schematic illustrations ofadditional techniques for anchoring prosthetic valve 10 at native valve12, in accordance with respective applications of the present invention.In these applications, prosthetic valve 10 comprises one or moresubvalvular anchoring elements 120, which are configured to piercenative leaflets 30 and pass through to a subvalvular space. Anchoringelements 120 are typically shaped and positioned to apply a forceagainst the ventricular surface of native leaflets 30, thereby holdingupstream annular skirt 26 against the native annulus. The anchoringelements are generally elongated (e.g., have a length of between 2 and 7mm), and may, for example, be shaped as hollow needles, solid needles,rods, or rectangular plates. The anchoring elements typically comprise ametal, such as Nitinol.

For some applications, as shown in FIG. 5A, distal ends of anchoringelements 120 are curved toward upstream annular skirt 26, and thustoward the ventricular surface of the native annulus when the prostheticvalve is implanted. For other applications, as shown in FIG. 5B, thedistal ends of the anchoring elements are folded. Alternatively oradditionally (i.e., optionally in combination with the application shownin FIG. 5A or the application shown in FIG. 5B), the distal ends of theanchoring elements are shaped so as to define respective barbs 124, asshown in FIG. 5C.

For some applications, as shown in FIG. 5A, the anchoring elements areconfigured to assume a curved shape when in resting states. In order tomore readily pierce the native leaflets, the anchoring elements areconfigured to initially assume a straighter shape during theimplantation procedure. For example, as shown as configuration “A” ofFIG. 5A, rigid rods 122 may be initially inserted into the lumens of theanchoring elements, which are shaped as hollow needles, in order to atleast partially straighten the anchoring elements. After the anchoringelements have penetrated the native leaflets, rods 122 are withdrawnfrom the anchoring elements, and the anchoring elements assume theircurved shapes, as shown as configuration “B” of FIG. 5A. For someapplications, an implantation tool is provided that comprises rods 122.This technique may additionally be used in combination with theapplication shown in FIG. 5B or the application shown in FIG. 5C.Alternatively or additionally, the anchoring elements comprises a shapememory alloy that is configured to initially assume a straighter shape,e.g., at a first temperature, and subsequently a curved shape, e.g., ata second temperature.

Reference is made to FIG. 6, which is a schematic illustration of yetanother technique for anchoring prosthetic valve 10 at native valve 12,in accordance with an application of the present invention. In thisapplication, prosthetic valve 10 comprises an elongated anchoring member152, such as a cord, strip, wire, or suture. Anchoring member 152 isconfigured to be positioned around at least a radial portion ofdownstream skirt 24 and be positioned in a subvalvular space 150. Whentightened, the anchoring member squeezes native leaflets 30 againstdownstream skirt 24, thereby fixing prosthetic valve 10 in place at thenative valve, and creating a seal between the valve prosthesis and thenative leaflets. For some applications, anchoring member 152 ispositioned completely around, i.e., surrounds, downstream skirt 24. Forsome applications, the anchoring member is introduced into thesubvalvular space and brought around the native leaflets using aguidewire that is introduced around the leaflets tangential to nativeannulus 32.

For some applications, valve prosthesis 10 further comprises acontracting housing 154. Typically, a first end of anchoring member 152is fixed to the contracting housing, and a second end of the anchoringmember passes through a channel of the contracting housing. Pulling onthe second end of the anchoring member tightens the anchoring memberaround the native leaflets. For some applications, an upstream portionof the anchoring member is shaped so as to define a ratchet, whichallows tightening, but not loosening, of the anchoring member.

Reference is made to FIG. 7, which is a schematic illustration of stillanother technique for anchoring prosthetic valve 10 at native valve 12,in accordance with an application of the present invention. In thisapplication, downstream skirt 24 is shaped so as to define a pluralityof anchoring arms 180, which extend in an upstream direction from adownstream end of downstream skirt 24 (as shown in FIG. 7), or fromlocations near the downstream end of the downstream skirt (configurationnot shown). The coupling arms are configured to be positioned in thesubvalvular space.

Prosthetic valve 10 is configured to assume two states: (a) an extended,unlocked state 182, shown as configuration “A” of FIG. 7, and (b) acontracted, locked state 184, shown as configuration “B” of FIG. 7. Alongitudinal length of prosthetic valve 10 along a central longitudinalaxis 186 thereof is greater when the prosthetic valve is in extended,unlocked state 182, than when the prosthetic valve is in contracted,locked state 184. The prosthetic valve is typically configured to allowone-way passage from unlocked state 182 to locked state 184. Forexample, mating downstream and upstream portions 188 and 190 ofdownstream skirt 24 may be shaped so as to define corresponding ratchetteeth 192, which allow downstream portion 188 to move in an upstreamdirection with respect to upstream portion 190, but not in a downstreamdirection with respect thereto.

During an implantation procedure, prosthetic valve 10 initially assumesextended, unlocked state 182. The prosthetic valve is advanced to nativevalve 12 in this unlocked state, and anchoring arms 180 are positionedsuch that native leaflets 30 are between the anchoring arms and the bodyof downstream skirt 24. The surgeon causes the prosthetic valve toassume contracted, locked state 184. In locked state 184 the anchoringarms squeeze and grasp native leaflets 30 and a portion of nativeannulus 32 between the anchoring arms, the body of the downstream skirt24, and upstream annular skirt 26. In this application, upstream annularskirt 26 may comprise relative short upstream arms 194, which maycorrespond to and be aligned with anchoring arms 180 of downstream skirt24. Optionally, upstream arms 194 may comprise one or more spikes 196,which are configured to pierce native annulus 32 in order to aid withanchoring.

FIGS. 8A-G are schematic illustrations of a valve contraction tool 200and a procedure for the use thereof, in accordance with an applicationof the present invention. Valve contraction tool 200 is optionally usedwith the configuration of prosthetic valve 10 described hereinabove withreference to FIG. 7, in order to cause prosthetic valve 10 to transitionfrom extended, unlocked state 182 to contracted, locked state 184.

As best seen in FIG. 8E, tool 200 comprises a catheter 220, and anupstream pushing tube (not shown), a downstream end of which is coupledto an upstream pushing adaptor 212. Upstream pushing adaptor 212 isconfigured to assume an umbrella-like shape when expanded, forming adownstream ring that is sized to rest and push against upstream annularskirt 26. Tool 200 further comprises a downstream pulling adaptor 214,which is coupled to a pulling wire 216. Downstream pulling adaptor 214is configured to rest against the downstream end of downstream skirt 24.Pulling wire 216 is coupled to the downstream pulling adaptor (e.g., ata center thereof), and passes through upstream pushing adaptor 212 andthe upstream pushing tube.

For some applications, a procedure using tool 200 begins with theintroduction of catheter 220, as shown in FIG. 8A. Catheter 220 isadvanced through the lumen of prosthetic valve 10, until a downstreamcap 222 of the catheter passes entirely through the prosthetic valve, asshown in FIG. 8B.

As shown in FIG. 8C, downstream cap 222 is extended downstream from adownstream adaptor holder 224, releasing downstream pulling adaptor 214from downstream adaptor holder 224. Upon release, downstream pullingadaptor 214 expands. Pulling wire 216 is pulled in an upstreamdirection, pulling downstream pulling adaptor 214 against downstreamportion 188 of downstream skirt 24, as shown in FIG. 8D.

As shown in FIG. 8E, upstream pushing adaptor 212 is deployed fromcatheter 220 against upstream annular skirt 26. In order tolongitudinally contract prosthetic valve 10, the surgeon pulls pullingwire 216 in an upstream direction, while simultaneously pushing on thepushing tube in a downstream direction. The pushing tube pushes upstreampushing adaptor 212 against upstream annular skirt 26, thereby holdingthe annular skirt against native annulus 32, and holding upstreamportion 190 of downstream skirt 24 stationary. Pulling wire 216 pulls ondownstream pulling adaptor 214, causing the downstream pulling adaptorto pull downstream portion 188 of downstream skirt 24 toward upstreamportion 190, thereby contracting the prosthetic valve.

Upstream pushing adaptor 212 is retracted into catheter 220, anddownstream pulling adaptor 214 is retracted into downstream adaptorholder 224, as shown in FIG. 8F. Pulling wire 216 pulls adaptor holder224 and downstream cap 222 against the body of catheter 220, and thecatheter is withdrawn from prosthetic valve 10, as shown in FIG. 8G.

Although prosthetic valve 10 has been described herein as beingconfigured for implantation in and/or at least partial replacement of anative atrioventricular valve, for some applications prosthetic valve 10is configured for implantation in and/or at least partial replacement ofa native aortic valve or a native pulmonary valve, mutatis mutandis.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present inventionincludes both combinations and subcombinations of the various featuresdescribed hereinabove, as well as variations and modifications thereofthat are not in the prior art, which would occur to persons skilled inthe art upon reading the foregoing description.

1. Apparatus comprising a prosthetic atrioventricular valve for couplingto a native atrioventricular valve, the prosthetic valve comprising: asupport frame; a covering, which at least partially covers the supportframe, wherein the support frame and the covering are shaped so as todefine a downstream skirt; a plurality of prosthetic leaflets, coupledto at least one element selected from the group consisting of: thesupport frame and the covering; and an elongated anchoring member,configured to be positioned around the downstream skirt in a subvalvularspace, such that the anchoring member presses native leaflets of thenative valve against the downstream skirt, thereby anchoring theprosthetic valve to the native valve.
 2. The apparatus according toclaim 1, wherein the elongated anchoring member is configured to bepositioned completely around the downstream skirt.
 3. The apparatusaccording to claim 1, wherein the prosthetic valve further comprises acontracting housing shaped so as to define a channel therethrough,wherein a first end of the anchoring member is fixed to the contractinghousing, and wherein a second end of the anchoring member passes throughthe channel.
 4. The apparatus according to claim 1, wherein theprosthetic valve is configured to assume collapsed and expanded states.5. Apparatus comprising a prosthetic atrioventricular valve for couplingto a native atrioventricular valve, the prosthetic valve comprising: asupport frame; a covering, which at least partially covers the supportframe, wherein the support frame and the covering are shaped so as todefine a downstream skirt; a plurality of prosthetic leaflets, coupledto at least one element selected from the group consisting of: thesupport frame and the covering; and a plurality of subvalvular anchoringelements, coupled to the downstream skirt, and configured to anchor theprosthetic valve to the native valve by piercing native leaflets of thenative valve, passing through to a subvalvular space, and applying aforce against the ventricular surface of the native leaflets.
 6. Theapparatus according to claim 5, wherein the prosthetic valve isconfigured to assume collapsed and expanded states.
 7. The apparatusaccording to claim 5, wherein each of the tissue coupling elements isshaped as an element selected from the group consisting of: a hollowneedle, a solid needle, a rod, and a rectangular plate.
 8. The apparatusaccording to claim 5, wherein the tissue coupling elements areconfigured to assume a curved shape when in resting states.
 9. Theapparatus according to claim 5, wherein the tissue coupling elements areshaped so as to define respective barbs.
 10. The apparatus according toany one of claims 5-9, wherein the tissue coupling elements compriseneedles.
 11. The apparatus according to claim 10, wherein the needlesare configured to assume curved shapes when in resting states.
 12. Theapparatus according to claim 11, wherein the needles are shaped so as todefine respective lumens, and wherein the apparatus further comprises animplantation tool, which comprises a plurality of rigid rods initiallypositioned in the lumens, respectively, so as to at least partiallystraighten the needles.
 13. The apparatus according to claim 11, whereinthe needles comprise a shape memory alloy.
 14. Apparatus comprising aprosthetic atrioventricular valve for coupling at a native valve, theprosthetic valve comprising: a support frame; a covering, which at leastpartially covers the support frame, wherein the support frame and thecovering are shaped so as to define an upstream annular skirt; aplurality of prosthetic leaflets, coupled to at least one elementselected from the group consisting of: the support frame and thecovering; a plurality of longitudinal members, coupled to the upstreamannular skirt at respective sites; and a plurality of tissue anchors,configured to be guided along the longitudinal members, respectively,and to couple the upstream annular skirt to cardiac tissue in a vicinityof the native valve.
 15. The apparatus according to claim 14, whereinthe prosthetic valve is configured to assume collapsed and expandedstates.
 16. The apparatus according to claim 14, wherein the tissueanchors are configured to pass over the respective longitudinal members.17. The apparatus according to claim 14, wherein the longitudinalmembers comprise respective wires, and wherein the tissue anchors areconfigured to be guided along the respective wires.
 18. The apparatusaccording to claim 14, wherein each of the tissue anchors comprises acoupling element that is shaped so as to define a shape selected fromthe group consisting of: a helix, a spiral, a corkscrew, and a screwshaft.
 19. The apparatus according to claim 14, wherein the longitudinalmembers are removably coupled to the upstream annular skirt at therespective sites.
 20. The apparatus according to claim 14, wherein theprosthetic valve further comprises a downstream skirt.
 21. The apparatusaccording to claim 14, wherein the prosthetic valve further comprises aventricular anchoring assembly, which comprises: a ventricular tissueanchor; and a ventricular longitudinal member, a first end of which iscoupled to the support structure, and a second end of which is coupledto the ventricular tissue anchor.
 22. A method comprising: providing aprosthetic atrioventricular valve, which includes (a) a support frame,(b) a covering, which at least partially covers the support frame,wherein the support frame and the covering are shaped so as to define adownstream skirt, (c) a plurality of prosthetic leaflets, coupled to atleast one element selected from the group consisting of: the supportframe and the covering, and (d) an elongated anchoring member; placingthe prosthetic valve at a native valve of a subject, such that thedownstream skirt passes through an orifice of the native valve toward aventricle of the subject; and anchoring the prosthetic valve to thenative valve by positioning the elongated anchoring member around thedownstream skirt in a subvalvular space, such that the anchoring memberpresses native leaflets of the native valve against the downstreamskirt.
 23. The method according to claim 22, wherein positioning theelongated anchoring member comprises positioning the elongated anchoringmember completely around the downstream skirt.
 24. The method accordingto claim 22, wherein the prosthetic valve further includes a contractinghousing shaped so as to define a channel therethrough, wherein a firstend of the anchoring member is fixed to the contracting housing, andwherein a second end of the anchoring member passes through the channel,and wherein anchoring further comprises pulling on the second end of theanchoring member to tighten the anchoring member around the nativeleaflets.
 25. The method according to claim 22, wherein placing theprosthetic valve comprises delivering the prosthetic valve to the nativevalve while the prosthetic valve is in a collapsed state in a catheter,and deploying the prosthetic valve from the catheter such thatprosthetic valve assumes an expanded state.
 26. A method comprising:providing a prosthetic atrioventricular valve, which includes (a) asupport frame, (b) a covering, which at least partially covers thesupport frame, wherein the support frame and the covering are shaped soas to define a downstream skirt, (c) a plurality of prosthetic leaflets,coupled to at least one element selected from the group consisting of:the support frame and the covering, and (d) a plurality of subvalvularanchoring elements, coupled to the downstream skirt; placing theprosthetic valve at a native valve of a subject, such that thedownstream skirt passes through an orifice of the native valve toward aventricle of the subject; and anchoring the prosthetic valve to thenative valve by causing the subvalvular anchoring elements to piercenative leaflets of the native valve, pass through to a subvalvularspace, and apply a force against the ventricular surface of the nativeleaflets.
 27. The method according to claim 26, wherein placing theprosthetic valve comprises delivering the prosthetic valve to the nativevalve while the prosthetic valve is in a collapsed state in a catheter,and deploying the prosthetic valve from the catheter such that theprosthetic valve assumes an expanded state.
 28. The method according toclaim 26, wherein each of the tissue coupling elements is shaped as anelement selected from the group consisting of: a hollow needle, a solidneedle, a rod, and a rectangular plate.
 29. The method according toclaim 26, wherein the tissue coupling elements are configured to assumea curved shape when in resting states.
 30. The method according to claim26, wherein the tissue coupling elements are shaped so as to definerespective barbs.
 31. The method according to claim 26, wherein placingcomprises placing the prosthetic valve such that the downstream skirtpushes aside and presses against the native leaflets.
 32. The methodaccording to any one of claims 26-31, wherein the tissue couplingelements include needles.
 33. The method according to claim 32, whereinthe needles are configured to assume curved shapes when in restingstates.
 34. The method according to claim 33, wherein the needles areshaped so as to define respective lumens, and wherein anchoringcomprises causing the subvalvular anchoring elements to pierce thenative leaflets while a rigid rods are initially positioned in thelumens, respectively, so as to at least partially straighten theneedles, and subsequently withdrawing the rods from the lumens.
 35. Themethod according to claim 33, wherein the needles comprise a shapememory alloy.
 36. A method comprising: providing a prostheticatrioventricular valve, which includes (a) a support frame, (b) acovering, which at least partially covers the support frame, wherein thesupport frame and the covering are shaped so as to define an upstreamannular skirt, (c) a plurality of prosthetic leaflets, coupled to atleast one element selected from the group consisting of: the supportframe and the covering, and (d) a plurality of longitudinal members,coupled to the upstream annular skirt at respective sites; placing theprosthetic valve at a native valve of a subject, such that the upstreamannular skirt rests against a native annulus of the native valve, andthe longitudinal members extend into an atrium of the subject; guiding aplurality of tissue anchors along the longitudinal members,respectively; and using the anchors, coupling the upstream annular skirtto cardiac tissue in a vicinity of the native valve.
 37. The methodaccording to claim 36, further comprising decoupling the elongatedmembers from the upstream annular skirt.
 38. The method according toclaim 36, further comprising, after placing the prosthetic valve at thenative valve and before coupling the upstream annular skirt to thecardiac tissue using the tissue anchors, temporarily anchoring theprosthetic valve to a ventricular wall of the subject using one or moreventricular cords.
 39. The method according to claim 36, wherein guidingcomprises passing the tissue anchors the tissue anchors over therespective longitudinal members.
 40. The method according to claim 36,wherein the longitudinal members include respective wires, and whereinguiding comprises guiding the tissue anchors along the respective wires.41. The method according to claim 36, wherein each of the tissue anchorsincludes a coupling element that is shaped so as to define a shapeselected from the group consisting of: a helix, a spiral, a corkscrew,and a screw shaft.
 42. The method according to any one of claims 36-41,wherein placing the prosthetic valve comprises delivering the prostheticvalve to the native valve while the prosthetic valve is in a collapsedstate in a catheter, and deploying the prosthetic valve from thecatheter such that the prosthetic valve assumes an expanded state. 43.The method according to claim 42, wherein placing the prosthetic valvecomprises placing the prosthetic valve at the native valve such that thelongitudinal members pass through the catheter.
 44. The method accordingto any one of claims 36-41, wherein the prosthetic valve furtherincludes a downstream skirt, and wherein placing comprises placing theprosthetic valve at the native valve such the downstream skirt passesthrough an orifice of the native valve toward a ventricle of thesubject.
 45. The method according to claim 44, wherein placing comprisesplacing the prosthetic valve such that the downstream skirt pushes asideand presses against native leaflets of the native valve.